Kurt Russell committed a “cardinal sin” on the set of the Guardians Of The Galaxy sequel after secretly sending a photo of himself in full costume to his family.

Studio bosses at Marvel are famous for keeping details about their superhero blockbusters under wraps, with cast and crew members often banned from taking photos on set, but Kurt couldn’t help himself because he was so stunned at how youthful his longtime make-up artist, Dennis Liddiard, made him look for flashback scenes at the beginning of Guardians of the Galaxy Vol. 2, in which the 66-year-old portrays Chris Pratt’s onscreen dad.

“I violated a cardinal sin (sic) ‘cause at Marvel, they really hold things close to the vest (keep things secret),” he told U.S. breakfast show Good Morning America. “For instance, I didn’t know my character’s name was Ego the Living Planet for the three weeks (I was shooting)...!”

“Anyway, I saw this (his younger self) and I had to, I took a picture, and I sent it to Goldie (Hawn, longtime partner) and the kids and said, ‘If you show this to anybody, I’ll be dead tomorrow, so you have to not do that! But look at this!’,” he smiled.

Liddiard did such a good job taking decades off Kurt, special effects experts didn’t have to do much when director James Gunn submitted the footage for touch-ups.

“It’s kind of amazing,” Kurt marvelled. “We assumed it would be pure CGI (computer-generated imagery) and all the magic it can do... (but) just before we went in there to start doing the physical aspect of it live, he (Liddiard) said to them (filmmakers), ‘You know, I know his face really well, and I can age him down a lot; I got a lot of tricks in my bag. Would that be helpful to you?’ And (James Gunn) said, ‘Sure, whatever you can do would be helpful.’”

“And so he went to work... and then we got the hair right, and the clothes...,” the actor continued. “We looked at (the finished appearance) and said, ‘This is gonna be great!’ So the woman who’s the head of the CGI department, at the screening (premiere) in L.A., she said, ‘What do you think about what we did to ya?’ I said, ‘Pretty great, but I understand it was more of a brush up here and there,’ (and) she said, ‘Yeah, he (Liddiard) did most of it!’ So all kudos to him.”